This invention relates to disposable containers or receptacles and associated lids of the type utilized for packaging "take-out" food products in restaurants, and the like. Such containers are often in the form of relatively shallow plates, and the associated lids are designed for removable attachment thereto to cover, protect, and retain heat (or cold) in the packaged food products.
Removal of the lids of such containers is often awkward, if not difficult. Moreover, with respect to many of such containers where the associated lid extends downwardly over the peripheral edge of the plate, it is a difficult task to remove the lid without also spilling the packaged contents. This is because the plate or container has little depth (or sidewall) which could otherwise be held with one hand while the lid is pried off with the other. It is also due in part to the effort required to remove the lid, and the unstable, or tilted, orientation of the container which is necessary to effectively exert such effort. In the prior art, several attempts have been made to overcome this and other related problems. For example, it is known to provide food containers with covers formed with rupturable, cut score lines in conjunction with an associated pull tab so that the cover can be torn off in a predetermined pattern. Configurations of this type are disclosed in U.S. Pat. Nos. 4,386,706; 4,184,605; 3,773,207; 3,572,579; 3,515,334; and 3,159,303.
In U.S. Pat. No. 3,391,852, a container construction is disclosed which includes a substantially planar lid held in place on the container by a peripheral fold-over flange.
In U.S. Pat. No. 3,836,039, an easy opening arrangement is provided for rigid or semi-rigid plastic sheet material wherein a tab is integrally formed in the cover, the tab being defined by a score line but wherein a portion of the tab is completely severed from the sheet material and covered with a patch of pressure-sensitive tape.
In U.S. Pat. Nos. 4,362,252 and 3,073,477 there are disclosed plastic containers having tear-off covers provided with pull tabs which act in conjunction with additional structure, excluding score lines, such that the cover will tear away from the container in a destructive first use.
In U.S. Pat. No. 3,980,224, opening means for containers and packages are disclosed wherein a cover, which may be sealed to an associated container, is constructed of a sheet containing at least one crystalline thermoplastic high molecular resin layer, the resin layer being partially uniaxially oriented, and further including an integral tab arranged to be pulled up in the uniaxially oriented direction whereby the sheet-like lid is torn into two parts.
In the present invention, a disposable container and associated lid of simplified construction are disclosed, wherein the lid is easily removable without any danger of spilling the contents of the container, because the container may be held in a level orientation with only minimal force required to remove the lid. At the same time, until the lid is removed, a liquid tight, or leak-resistant sealing relationship is maintained between the lid and the container to prevent leakage or seepage of food liquids (gravies, juices, etc.) when the lidded container is transported from point-of-purchase to destination.
In another aspect of the present invention, the disposable lids, as well as assembled containers and lids, are stackable to facilitate shipping, storage, etc.
In an exemplary embodiment of the invention, a lid is formed with a generally planar, sunken area, surrounded by an upstanding rim and a depending, peripheral skirt. The lower portion of the skirt is formed with a specific profile which includes a stacking ring for permitting stacking of a plurality of individual lids; a sealing ring for establishing a liquid tight or leak resistant seal between the lid and the outer peripheral edge of an associated plate-like container; and a snap ring for initially engaging and holding the plate and lid in assembled relationship. In addition, the lid is provided with an integral pull tab extending outwardly from the lowermost edge of the lid.
The lid is further provided with three distinct means by which tearing of the lid in a generally predetermined fashion is assured upon upward pulling of the integrally formed tab.
The first of these relates to the plastic material of which the lid is constructed. In a preferred embodiment, the lid is composed of an amorphous polymer, such as impact polystyrene. Another suitable plastic material is a styrene-butadiene copolymer known as K-resin.TM., made by Phillips Petroleum. The lid may also be constructed of a blend of K-resin.TM. and general purpose polystyrene (no impact) which is advantageous in that it is less costly than 100% K-resin.TM., and tends to be more susceptible to orientation stresses, thus enabling the tab to work more easily. It is known that the molecules of such plastic materials tend to uniaxially orient themselves in the direction in which they are pulled from the plastics forming machine, and that the plastic is very weak in a direction transverse to the orientation direction. Accordingly, the disposable lid is formed with the molecules oriented such that the lid is susceptible to tearing upon upward pulling on the tab, thus enabling easy removal from the container, with little if any likelihood of spillage.
Tearing is also facilitated by the incorporation of a rectangular projection at the interface of the pull tab and the depending skirt. This projection, in effect, interrupts or erases the snap ring along an area substantially commensurate with the width of the pull tab. The immediate effect of this arrangement is to eliminate the need for the tear to extend through the tortuous cross-section of the lid at the snap ring, and to direct the tear substantially vertically upwardly.
Finally, tearing of the lid is facilitated by a slight notching on either side of the pull tab which eliminates the need for the strong force normally required to at least initiate tearing action.
Accordingly, the present invention provides a simple, inexpensive, disposable lid and container for food products and the like, which maintains an effective liquid tight or leak resistant seal between the container contents and the exterior environment, and which is easy to remove with virtually no danger of spillage.
Other objects and advantages of the subject invention will become apparent from the detailed description of the invention which follows.